Commonly, the position of an overhead garage door is determined based on three types of sensors: end limit switches, a tilt switch, and an accelerometer. The end limit switches determine whether the garage door is completely closed, fully open, or somewhere in between. The tilt switch will only trigger at one particular angle based on the angular position of the tilt switch. In many garage door control systems, the tilt switch cannot be used to identify or determine a partially closed or partially opened position of the garage door. For example, if the garage door is left partially open, the tilt switch may not be able to signify open until the garage door has opened past the point where someone can sneak in under the gap.
The accelerometer can be used to tell the angle of the garage door and can work well for one-piece garage doors (also known as California garage doors). However, for a segmented door, the accelerometer can be placed on any segment, section, or panel. For example, if the accelerometer is placed on the top panel, the sensor is very good at determining that the garage door is open just a little bit, but often is unable to determine the difference between that little bit and all the way open. The opposite is true for the bottom segment.
Therefore, the use of limit switches, a tilt switch sensor, or an accelerometer may not be useful in determining the position of an overhead garage door as the door is opening/closing.